A resident walks through flood water and past a stalled ambulance in the aftermath of Sandy in Hoboken, N.J. / By Charles Sykes, AP

by Dan Vergano
USA TODAY
@dvergano, USA TODAY

by Dan Vergano
USA TODAY
@dvergano, USA TODAY

Haven't we been here before? A hurricane devastates a major coastal city, and a debate over climate change comes in like the tide.

Will the warnings about sea-level rise in the wake of Hurricane Sandy wash away like the concern seen after Hurricane Katrina devastated New Orleans in 2005? Or has the tide finally risen too high to ignore?

"Our climate is changing," said New York Mayor Michael Bloomberg, a political independent, in a statement on Thursday. Bloomberg endorsed President Obama's re-election in his statement, and cited the president's climate views as a reason.

"While the increase in extreme weather we have experienced in New York City and around the world may or may not be the result of (climate change), the risk that it might be - given this week's devastation - should compel all elected leaders to take immediate action," Bloomberg said.

In the aftermath of Hurricane Sandy, now blamed for 170 deaths and perhaps $50 billion in damages by the disaster firm EQECAT of Oakland, a fight immediately broke out over the role of global warming in the storm.

"Mostly, it's a natural thing,"climate scientist Gerald North of Texas A&M called the storm in an interview with the Associated Press. Others, such as Texas Tech climate scientist Katharine Hayhoe, noted that warmer Atlantic waters and Arctic weather that helped steer the storm were juiced by global warming and played a significant role. (Hayhoe notes that this is basically climatologists seeing two sides of the same coin, as both her and North agree the storm was mostly natural but with contributions from climate change.)

Global warming has contributed a roughly 1.4-degree Fahrenheit increase to global average surface temperatures over the last century, according to a 2010 National Academy of Sciences report, largely driven by burning fossil fuels that release warming "greenhouse" gases to the air. Although hurricanes look less frequent in a warmer world, warmer waters would strengthen the storms that happen and high sea levels, obviously, would lead to higher storm surges.

The unusual nature of Hurricane Sandy, which switched from a standard hurricane to a winter storm arriving at high tide along the East Coast, added to disagreement. "While we do expect increased hurricane damage in the U.S. as the climate warms, Sandy is not a pure example of a hurricane," said MIT climate scientist Kerry Emanuel. Unfortunately, scientists haven't looked hard at the climate's effects on such "hybrid" storms, says Emanuel.

"Until we have done more work on this problem, it is not possible to say much about how hybrid storms will respond to climate change."

But there is little disagreement that sea levels worldwide average about a foot higher than a century ago due to seawater expanding in a warming ocean in the face of climate change. Sea levels will rise at least 2 feet this century, according to the 2007 Intergovernmental Panel on Climate Change report. Experts such as geologist William Hay of the University of Colorado-Boulder, still call that too conservative, seeing at least another 3 feet of sea-level rise as inevitable. That extra increase is due to ice sheet melting in Greenland and elsewhere, which was not accounted for in the 2007 report.

Sandy arrived with 14- to 15-foot waves overtopping the "500-year storm" flood zoning height limits of 10.7 feet set for New York City. As a result, every extra foot of sea-level rise looks unwelcome.

"What we shouldn't lose sight of is the flooding that has taken place in major cities around the world in the last few years," says Alan Weisman, author of The World Without Us, a book that looked at the herculean task of maintaining our cities and homes against the forces of nature. Bangkok, Manila and Guangzhou (or Canton) in China have flooded in recent years, he notes. Combining rising seas with overbuilt cities poses constant risk of disaster, Weisman warns. "This is just one storm, terrible as it was. What happens when there are more of them?"

Although links between extreme weather events and climate change remain controversial, they do have an effect on public opinion, say experts. "I suspect Sandy will be interpreted by a majority of Americans as further evidence that global warming is destabilizing our weather," says climate opinion pollster Edward Maibach of George Mason University in Fairfax, Va.

However, similar increases in concern seen after Hurricane Katrina faded, notes sociologist Robert Brulle of Drexel University in Philadelphia, a visiting scholar at Stanford University. "Will it fade again? The answer will be whether political leaders continue to talk about climate after Sandy fades and the (presidential) election is over," Brulle says. If more politicians such as Bloomberg and New York Gov. Andrew Cuomo continue to speak out on climate concerns, public opinion research suggests the issue remains alive in the public mind, Brulle says. "We'll know in three weeks if they are still talking about it," he says. "That will really tell us if climate concerns will stick with people."